The present invention is directed to a method for generating trigger or ignition pulses for an internal combustion engine.
In addition to a prescribed control or trigger delay angle at which a periodic event should be executed, motor control systems also require information about the respective relative or angular position of the crank shaft or of the cam shaft with respect to a reference mark such as, for example, the upper dead point. This is in order to generate trigger or ignition pulses that control a periodically repeating event of an internal combustion engine, such as, for example, regarding ignition the beginning of the closing or dwell angle fuel injection. For example, a toothed disk that senses a generator is attached to the crank shaft for this purpose. This generator supplies angular signals that correspond to the respective angular or relative position of the crank shaft.
The tooth pitch of this toothed disk defines the smallest possible resolution, i.e. a smallest possible range between two angular positions that can be distinguished by the generator. Trigger delay angles lying therebetween can only be identified on the basis of a preliminary calculation.
When the crank shaft has traversed one of the allowed ranges, a calculated running time that it requires for traversing the next, successive allowed range is required for such a preliminary calculation. It is thereby assumed that the internal combustion engine continues to move with a constant speed. The calculated running time then is determined from a linear extrapolation. The point in time at which the trigger delay angle is reached is finally calculated by a linear interpolation into this allowed range.
When, however, the internal combustion engine is accelerated or retarded so that the speed changes, then an error that increases with the degree of the acceleration o retardation will arise in this preliminary calculation. The error is greater, for greater allowed ranges, so that optimally highly resolving toothed disks must be used.